The Prime Minister has a substantial amount of task every day. The Cabinet Secretariat provides direct support to the Prime Minister and is involved in the operations including planning and framing, overall coordination of important policies of the Cabinet, general affairs of the Cabinet, collection and research of intelligence, and management of the Prime Minister's Official Residence.

Specifically, the Cabinet Secretariat fulfills a comprehensive strategic function. Under the leadership of the Prime Minister and through various Cabinet meetings and councils, the Cabinet Secretariat makes the supreme and final adjustments, and plans and drafts the basic government policies on the important policy of the Cabinet of the time such as administrative reform and Special Zones for Structural Reform.

In addition, the Cabinet Secretariat, with a view to facilitating the management of Cabinet meeting and administrative vice-minister level meeting, serves as the organ of the Cabinet such as to organize cases that will be brought up for discussion in Cabinet meeting and others, and to fulfill a role of corresponding secretary in cases when the Cabinet submits the budget or legislative bills to the Diet. The duty of the Cabinet Secretariat also includes public relations activities including maintaining the website of the Prime Minister of Japan and His Cabinet and the Koizumi Cabinet Mail Magazine.